The present invention primarily relates to a driving mechanism for a human-powered vehicle such as a bicycle, a wheelchair, a boat, or a human-powered airplane, or a human-powered machine comparable to a human-powered vehicle, for example, a muscle training machine.
The driving mechanism for a bicycle and the driving mechanism for a leisure recreational pedal boat are identical in principle. Both driving mechanisms comprise a rotational axle, two cranks, or the left and right cranks, and a pair of pedals. More specifically, the two cranks are rendered different in rotational phase by 180xc2x0, with one end of each crank being fixed to the rotational axle at a right angle. The other end of each crank is provided with a shaft, which is anchored to the crank at a right angle, and around which a pedal is rotationally fitted. Torque is generated as an operator steps on the pedal, and this torque is used to rotate the propelling means, such as a wheel, a propeller, or the like, of a human-powered vehicle to move the vehicle. In recent years, there have appeared a tricycle and a four-wheel-cycle, in addition to a bicycle, and they seem to have been used even for competitive sports, in Europe and the United States. However, the driving mechanism for a human-powered vehicle has not changed at all in principle.
A bicycle is very widely used as means for recreation, means for commuting to and from school or work, and means for competition, and therefore, the bicycle industry is very large. Here, the present invention will be described with reference to a bicycle for the sake of simplicity.
A bicycle has been developed in accordance with its usage, and therefore, there are many kinds of bicycles different in structure and appearance. As far as the present invention is concerned, which relates to a driving mechanism for a human-powered vehicle, there are bicycles equipped with a speed changing mechanism for improving a bicycle in speed and climbing performance. There are various speed changing mechanisms. Basically, they comprise a plurality of sprockets attached to a follower axle, that is, the rear wheel axle (hereinafter, this type of sprocket will be referred to as xe2x80x9cfollower axle sprocketxe2x80x9d), and only a single sprocket attached to the driving axle by a chain, whereas some of them comprise a plurality of sprockets attached to the driving axle (hereinafter, this type of sprocket will be referred to as xe2x80x9cchain ringxe2x80x9d), and the aforementioned follower axle sprockets, which are connected to each other by a chain. Also widely used in the field of a human-powered vehicle are driving mechanisms equipped with a planetary gear mechanism attached to the follower axle. It should be noted here that in this patent application, the human-powered vehicle driving mechanism means a driving mechanism for transmitting human power to the speed changing mechanism of a human powered vehicle, or the propelling means, for example, a wheel, a propeller, and the like, of a human-powered vehicle.
In principle, a speed changing mechanism does not improve energy conversion efficiency, regardless of its configuration. In other words, it does not increase the total amount of the power transmitted to a propelling means (bicycle rear wheel, boat propeller, and the like), or reduce the total amount of energy consumed by a driver per hour.
If an attempt is made by a bicycle rider to climb a slope using the same speed increasing ratio as that used when the rider is running on flat land, a xe2x96xa1larger force is necessary, and whether or not the rider can continue riding the bicycle is determined by the strength of the legs of the rider. To the rider, a speed changing mechanism is an apparatus for trading the speed of applying force for the applied force, or an apparatus for optimizing the balance between speed of applying force and the applied force. In other words, if the muscular force becomes insufficient upon uphill riding, the speed changing mechanism is down-shifted to reduce the speed increasing ratio, allowing the muscles to move at a higher speed with a smaller amount of force, and yet producing the same amount of power. However, reducing the speed increasing ratio below a certain level is meaningless. That is, as the speed increasing ratio is reduced in order to keep the bicycle running, the rider must pedal faster to rotate the driving axle faster in reverse proportion to the decrease in the speed increasing ratio, which in turn causes the rider to reach his or her limit in physical capacity, and also increases the friction and/or vibrations for which the bearings and chain of the driving mechanism are responsible. Eventually, it becomes impossible for the rider to keep the bicycle balanced to continue riding.
The provision of a speed changing mechanism does not guaranty increase in the power input. Thus, it is obvious that there is a limit in the improvement in slope climbing performance. Therefore, a means for increasing the power input by a rider has been desired. Here, the power input by a rider means the amount of the power (amount of work per unit of time) transmitted from the rider of a bicycle, that is, a human-powered vehicle, to the bicycle through the driving mechanism of the bicycle. In a speed changing mechanism, the revolution of its output shaft is in inverse proportion to the amount of the torque output through the output shaft, the product of the two (revolution of the output shaft and the amount of the torque output through the output shaft) remains constant. In other words, a speed changing mechanism allows the speed increasing ratio, that is, the balance point between the muscular speed and force, to be changed in accordance with the physical capacity of a rider and the riding conditions, in the direction to allow the rider to feel more comfortable. In principle, however, a speed changing mechanism does not change the overall amount of the power input by a rider, and therefore, the overall amount of the power output through the output shaft does not change.
Changing the length of a crank results in a trade-off between the speed at which a rider moves his or her muscles, and the amount of muscular force generated by him or her per pedaling stroke. Optimizing the crank length sometimes results in a small amount of increase in output, but this does not mean increase in input.
There are a certain number of inventions regarding the above described driving mechanism for a human-powered vehicle, for which patent applications have been submitted (U.S. Pat. Nos. 4,125,239, 4,706,516, 4,807,491, and the like). According to them, the cranks of a bicycle are configured so that they can be lengthened or shortened, and the rotational phases of the cranks are synchronized with the lengthening or shortening of the cranks with the use of a planetary gear based mechanism or a cam based mechanism so that the cranks become longest when they are horizontally extending forward to increase the amount of the maximum torque input by the rider.
In the case of the above described driving mechanism for a human-powered vehicle, as one of the pedals moves past the position where the crank to which the pedal is attached is horizontal, it enters a part of its rotational range in which the crank to which the pedal is attached begins to shorten. In this rotational range of the pedal, the force which acts in the radial direction of the locus of the pedal shaft, that is, a component of the force input by the rider through the pedal, drastically increases and resists the shortening of the crank, interfering with the rotation of the crank.
Even in the case of the human-powered vehicle driving mechanism described above, as long as the force applied to a pedal is always made to act tangential to the locus of the pedal shaft, this force does not interfere with the rotation of the crank. Actually, however, the ankle joints, knee joints, and hip joints, are limited in their ranges of movement, and therefore, the force applied to the pedal always acts downward in the virtually vertical direction regardless of rotational angle of the crank. Thus, when a crank is virtually horizontally extending forward, the tangential line to the locus of the pedal shaft and the direction in which the force is applied to the pedal virtually coincide with each other, and therefore, the magnitude of the xe2x80x9ctorque,xe2x80x9d that is, the component of the force applied to the pedal, which acts in the direction to rotate the pedal about the driving axle becomes maximum.
However, as the pedal moves past the point which corresponds to the virtually horizontal forward position of the crank, the torque (more precisely, the force which acts in the rotational direction of the crank, that is, a component force of the resultant force of the gravitational force, inertial force, and muscular force,) reduces, whereas the component force perpendicular to the rotational direction of the crank (more precisely, the force which acts in the longitudinal direction of the crank, that is, a component force of the resultant force of gravitational force, inertial force, and muscular force), that is, the force which acts in the direction to lengthen the crank against the force which acts in the direction to shorten the crank, increases, creating an effect equivalent to the effect of a mechanical brake. Thus, as far as a single rotational cycle of the crank is concerned, this structural arrangement for a human-powered vehicle driving mechanism has not increased power output in practical terms.
As an invention similar to the aforementioned human-powered vehicle driving mechanism, in which the crank length are rendered variable, there is U.S. Pat. No. 4,872,695. According to this patent, the driving mechanism comprises a rear wheel fork, a pair of bearings, a pair of connecting rods, a pair of cranks, and a pair of pedals. The bearing is pivotally attached to the rear wheel fork, and one end of the connecting rod is slidably fitted in the bearing. The end portion of the crank is rotationally connected to the connecting rod, at a point slightly toward the end portion with respect to the center, and the pedal is attached to this end portion of the rod. Thus, as a rider steps on the pedal, the connecting rod acts as a lever having the bearing as its fulcrum, amplifying the applied force from the rider as it is transmitted to the crank.
According to this cited invention, the applied force from the rider is amplified regardless of the rotational angle of the crank, and therefore, the torque definitely increases while the crank is in the portion (hereinafter, down stroke period) of its rotational range in which the pedal moves from its highest position (so-called top dead center) to its lowest position (so-called bottom dead center). However, while the crank is in the portion (hereinafter, up stroke period) of its rotational range in which the pedal moves from its lowest position to its highest position, negative torque is amplified. During the latter period, xe2x80x9cleveragexe2x80x9d is greater than during the former period; in other words, the ratio at which negative torque is amplified is greater than the ratio at which positive torque is amplified. Thus, as far as the entirety of a single pedaling cycle is concerned, increase in power output cannot be expected even in the case of the structural arrangement disclosed in the cited patent.
FIG. 13 is a graph created by modifying FIG. 7.3 in High-Tech Cycling (Human Kinetics, P.O. Box 5076, Campaign, Ill., USA) in order to effectively describe the present invention, and shows the relationship between the rotational force (the tangential component of the force acting on a pedal) and crank angle. The change of the rotational force while an American bicycle racer was pedaling with a power of 350 W (which appears to represent the amount of work effected upon the crank per unit of time, although no clear definition is given in the above document), at 90 rpm, is plotted on the axis of ordinates, and the crank angle xcex8 (clockwise angle with reference to the top dead center) is plotted on the axis of abscissas. According to this graph, the rotational force is highest when the crank angle xcex8 is slightly greater than 90xc2x0, and begin to rapidly reduce as the crank angle xcex8 is beyond approximately 120xc2x0.
A fact that the rotational force reduces while the crank angle xcex8 is in a range of 120xc2x0 less than xcex8 less than 180xc2x0, in which a sufficient portion of the combination of the weight of the lower limb and the muscular force, acted on the pedal, indicates that during this period, the combination of the weight of the lower limb and the muscular force acts overwhelmingly in the direction to stretch the crank, instead of the direction to rotate the crank. As a result, the energy of the rider is consumed to stretch the crank which could not be stretched. In other words, no matter how large the force applied to the pedal is, as long as the force is caused to act in the direction to stretch the crank, the amount of work accomplished is zero in terms of dynamics. However, within the body of the rider, blood rapidly circulates, and chemical reactions rapidly occurs, while consuming the energy of the rider. On the other hand, in a range of 217xc2x0 less than xcex8 less than 345xc2x0, the rotational force is negative. This is due to the fact that in a range of 180xc2x0 less than xcex8 less than 360xc2x0, the amount of the muscular force which acts in the direction to forwardly rotate the crank, and the weight of the limb which acts in the direction to reversely rotate the crank, equalized at a crank angle of approximately 200xc2x0, and eventually, the latter exceeded the former.
The human-powered vehicle driving mechanism disclosed in Japanese Laid-Open Patent Applications 58-133986, 58-221783, and 8-113180 comprise a pair of, that is, left and right drive trains, driving sub-mechanisms made up of a combination of a rope and pulleys, a combination of reciprocable chain and sprockets, and a rack and a pinion gear, correspondingly. In these driving mechanisms, the left and right drive trains are mechanically connected to each other in such a manner that when one side is in the forward stroke, the other side is in the backward stroke (incidentally, the names used for the above described driving mechanism components were arbitrarily chosen by the inventors of the present invention for convenience in describing the components, and they do not necessarily match the names used in the original specifications). For example, as the pedal of the left drive train is stepped in its forward stroke, the applied force is transmitted to the pulley, sprocket, and pinion gear through the rope, chain, and rack, correspondingly, and therefore, the wheels connected to the pulley, sprocket, and the pinion, correspondingly, rotate. When the left drive train is in the backward stroke, the pedal of the left drive train is lifted by the power from the right drive train. Also during this period, the pulley, sprocket, or pinion gear in the left drive train is allowed to idle relative to the output shaft, by a free wheeling mechanism, such as a rachet or one-way clutch, with which their shaft portions are provided.
Whichever of the above described inventions is used, during the forward stroke, human power acts in the direction tangential to the pulley, sprocket, or pinion gear, and therefore, the entirety of the applied force equals to the rotational force (converts into torque). However, at the end of the forward stroke, the movement of the lower limb is suddenly stopped while moving in the positive direction, and therefore, the kinetic energy of the lower limb, chain, rack, sprocket, pinion gear, and the like is forced to become zero. Thus, in terms of the entirety of each pedaling cycle, a significant amount of increase in output cannot be expected from the driving mechanism in accordance with any of the aforementioned inventions.
Japanese Laid-Open Patent Application 58-199279 discloses an invention, according to which the driving mechanism is rendered reciprocal with the employment of a combination of a chain and a sprocket, and a spring is made to absorb a part of the energy transmitted as a rider steps on a pedal, so that the pedal is returned to the pre-stepping (original) pedal position, by the energy stored in the spring. However, this invention also has a problem in that unless the pedaling motion is not synchronized with the free spring movement, increase in the output cannot be expected (if the pedal is stepped on before it fully returns, a sufficient distance is not available for pedal acceleration to have positive work even in the case of this invention, the initial pedal speed, or the pedal speed at the very moment the pedal begins to be stepped on, is considered to be 0 m/s), and therefore, a significant amount of increase in bicycle speed cannot be expected.
A certain number of studies have been done regarding a human-powered vehicle driving mechanism, which have noted the fact that a muscle generates larger force when it is contracted at a low speed than when it is contracted at a high speed. According to these studies, the chain ring, which normally is truly circular, was made elliptic or the like, and the relationship in the rotational phase between the chain ring and crank was devised to reduce the fluctuation in the crank revolution, so that a rider can apply a larger amount of muscular force to a pedal. However, this method has also a problem in that if the aforementioned relationship in the rotational phase between the chain ring and crank is fixed, the usage of the bicycle is limited. For example, a certain phase difference, which may be suitable for riding a long distance at a constant speed, may not be suitable for riding up a slope or riding at full speed.
The object of the present invention is to solve the problems in the above described prior technologies, so that it becomes possible to provide a driving mechanism which is capable of efficiently converting human power into driving force, and therefore, is most suitable for a human-powered vehicle such as a bicycle, a tricycle, a four-wheel-cycle, a wheelchair, a boat, a human-powered air plane, or a driving mechanism for a device comparable to a human-powered vehicle, for example, a muscle training device.
The first invention provides a human powered drive mechanism comprising a rotatable member, a supporting member, an endless driving member extended around said rotatable member and said supporting member, and a human powered drive receiving portion mounted to said endless driving member.
The second invention provides a human powered drive mechanism according to the first invention, wherein said supporting member is rotatable.
The third invention provides a human powered drive mechanism according to the first invention, wherein said endless driving member is movable along a large curvature radius portion, first and second small curvature radius portions, and said endless driving member is extended around said supporting member and said rotatable member at the first and second small curvature radius portions.
The fourth invention provides a human powered drive mechanism according to the first invention, further comprising constraining means for constraining rotation of said drive receiving portion about a line included in a plane in which the endless driving member moves.
The fifth invention provides a human powered drive mechanism according to the first invention, wherein said drive receiving portion is rotatable about an axis substantially perpendicular to a plane in which said endless driving member moves.
The sixth invention provides a human powered drive mechanism comprising a first rotatable member, a first supporting member, a first endless driving member extended around said first rotatable member and said first supporting member, a second rotatable member, a second supporting member, a second endless driving member extended around said second rotatable member and said second supporting member, a first human powered drive receiving portion mounted to said first endless driving member and a second human powered drive receiving portion mounted to said second endless driving member, wherein said first rotatable member and second rotatable member are coaxial with each other and are fixed to each other by a shaft member, said shaft member comprising a third rotatable member between said first and second rotatable members.
The seventh invention provides a human powered drive mechanism according to the first invention, wherein said constraining means includes an arm having one end rotatably mounted to said drive receiving portion and a free crank having one end rotatably mounted to a frame and the other end rotatably mounted to the other end of the arm. The eighth invention provides a human powered drive mechanism for a human powered vehicle comprising a propulsion wheel, a rotatable member, a supporting member an endless driving member extended around said rotatable member and said supporting member, and a human powered drive receiving portion mounted to said endless driving member, wherein said propulsion wheel is connected with said rotatable member.
The ninth invention provides a human powered drive mechanism according to the first invention, wherein a rotation axis of said free crank is disposed outside an orbit formed by said endless driving member. The tenth invention provides a human powered drive mechanism comprising a first rotatable member, a first supporting member, a first endless driving member extended around said first rotatable member and said first supporting member, a second rotatable member, a second supporting member, a second endless driving member extended around said second rotatable member and said second supporting member, a first human powered drive receiving portion mounted to said first endless driving member and a second human powered drive receiving portion mounted to said second endless driving member, wherein said first rotatable member and second rotatable member are coaxial with said propulsion wheel.
The eleventh invention provides a human powered drive mechanism according to the eighth invention, wherein said human powered vehicle is a bicycle.
The twelfth invention provides a human powered drive mechanism according to the eighth invention, wherein an inclination angle of a large curvature radius portion of said endless driving member relative to the ground is variable.
The thirteenth invention provides a human powered drive mechanism according to the fourth invention, wherein said endless driving member includes a plurality of links, and one of said links constitutes a driving force receiving link, wherein said driving force receiving link is provided with a shaft projected in a direction perpendicular to a plane in which said endless driving member moves, and said driving force receiving link is rotatably mounted to said constraining means through the shaft.
The fourteenth invention provides a human powered drive mechanism according to the thirteenth invention, wherein the shaft is integral with said driving force receiving link, and is rotatable relative to said constraining means.
The fifteenth invention provides a human powered drive mechanism according to the thirteenth invention, wherein said driving force receiving link is provided with a U-shaped groove, in which said driving force receiving link is rotatably connected with an adjacent link of said endless driving member.
The sixteenth invention provides a human powered drive mechanism according to the thirteenth invention, wherein said driving force receiving link is rotatably mounted to said constraining means by a roller bearing or a linear motion bearing such as a linear bush or the like.
In this specification, the rotatable member means a sprocket or a pulley for driving a load by being rotated by the endless driving member, and the supporting member means an arcuate guiding rail on which the endless driving member is extended circumferentially or a rotatable member on which the endless driving member is extended or trained and which rotates fundamentally idly. In the present invention, the endless driving member means a flexible member such a belt, timing belt, chain, bead chain, pinned chain, rope or the like, which is substantially freely collapsible and bendable but is not free against tensile force to permit transmission of a rotational force. The human powered drive receiving portion means a pedal, handle or the like to which the human power is directly applied. The frame means a member supporting the vehicle and forming the structure, or a structural member such as a pipe, a gauge steel, plate or the like.
The large radius curvature portion may have a radius of curvature which is infinite, that is, it may be linear, or the portion may be a slightly curved defined by a guiding rail or by an idle sprocket or the like.
According to the human powered drive mechanism of the present invention, the pair of the rotatable member and the supporting member can be located at an angle and a position with which the user can easily impart the force along the large radius curvature portion of the endless driving member through the human powered drive receiving portion, so that 100% of the human power can be converted to the driving torque at the large radius curvature portion, and the maximum level of the rotational force continues for a predetermined period of time, and in addition, at an end portion of the large radius curvature portion, the kinetic energy of the moving mass is converted to a rotational energy at the small curvature radius portion and is reserved. As a result, a significant increase of the power input is accomplished.
Because of the increase of the power input, the uphill performance is significantly improved such that changing speed mechanism is not necessarily required on a normal road.
The preferred human powered drive mechanism of the present invention comprises a chain having a pedal or a handle, a rotatable member and a supporting member along which the chain is trained, the pedal or the handle is maintained, by the constraining means, substantially perpendicular to the movement surface of the chain. Further preferably, the supporting member is in the form of a rotatable member.
In such a case, even if a force is imparted to the pedal or the handle, the chain is not bent or twisted, and therefore, the chain is protected from deformation or damage. Additionally, the position of the force acting point is determined so that application of force is easy with less muscle and joint fatigue.
In that case, it is preferable that the constraining means comprises a free crank rotatably mounted to the frame at an end thereof and an arm rotatably mounted to the other end of the free crank, and the arm is rotatably mounted to the drive receiving portion. Since the arm is rotatably mounted to the drive receiving portion, the rotation of the arm does not obstruct the motion of the chain, or the chain does not receive abnormal force. The advantage of the constraining means of this type is in that use can be made, for support and connection for the free crank and/or the arm, with a ball bearing, cylindrical roller bearing or needle bearing with which the frictional loss is very small and which is light in weight and small in size and with which the dust sealing is easy.
Further preferably, at the connecting portion between the arm and the chain, at least an outer ring of a cylindrical roller bearing or needle bearing is mounted to an end of the arm, and the chain is provided with a driving force receiving link, which is inserted into the outer ring with the rollers therebetween. The chain comprises a great number of chain links to permit continuous rotation. It is preferable that one of the chain links functions as the driving force receiving member.
It is preferable that relative motion in the axial direction is permitted between the outer ring of the bearing mounted to the end of the arm and the driving force receiving link inserted into the ring, since then the weights of the arm, crank and frame are reduced. When an attempt is made to reduce the weights of the arm, crank and frame, less rigidities tend to result, so that trace of revolving of the pedal about the line included in a plane in which the chain moves becomes relatively large due to the less rigidities, and therefore, when the pedal approaches to the sprocket, the link plates in the chain tend to strongly hit the side surfaces of the sprocket, even though the constraining means satisfies the original purpose not to give damages to the chain.
By selecting a cylindrical roller bearing, a needle bearing, a linear motion bearing (such as a linear bush bearing or the like) or the like, in which the shaft is supported for rotation and for axial displacement, so that only the pedal is displaced solely in the axial direction, by which the driving force receiving link is kept perpendicular to the chain moving plane, thus preventing the strong hit of the chain to the side surfaces of the sprocket. When the arm, the crank and the frame supporting the crank have sufficient rigidities, the relative displacement in the axial direction between the driving force receiving link and the arm may be prevented by employing a deep groove ball bearing or the like for the connecting portion between the arm and the chain.
Another example of the constraining means includes a combination of a free crank and a linear bush bearing or a ball spline linear bearing, exhibiting a small friction loss, in addition to the above-described combination of the free crank and the arm. However, the system is applicable when the radii of the rotatable member and the supporting member which constitute a pair are equal. More particularly, the structure using a combination of a linear bush bearing and a free crank comprises parallel arranged two rods with a certain length disposed inside the oval orbit formed by the chain and a reciprocating slider supported by the two rods through at least one linear bush bearing for each rod, and a free crank rotatably supported by the slider at one end around an axis perpendicular to the surface formed by said oval track which is rotatably supporting a pedal or a handle at the other end. The structure using a combination of a ball spline and a free crank comprises a linear bush rotatably affixed to a point on the bicycle frame, and a spline rod slidably supported by said bush at one end and rotatably supporting a pedal shaft or a handle shaft at the other end.
According to an embodiment of the present invention, the center of rotation of the free crank is disposed inside the oval orbit formed by the chain. In this case, it is further preferable that center of rotation of the free crank is disposed at the center of a line connecting centers of the rotatable member and the supporting member which constitute a pair. By doing so, the sum of the radius of rotation of the free crank and the radius of rotation of the arm is minimum, so that bending and torsion of the free crank and the arm are small, and therefore, the weight saving is accomplished.
In another example of the position of the center of rotation of the free crank, the center of rotation of the free crank is disposed outside the oval orbit formed by the chain. In this case, when the radius of the pitch circle of the rotatable member and the radius of curvature of the supporting member (the radius of a pitch circle if the supporting member is in the form of a rotatable member), which constitute the pair, are the same, the rotational axis of the free crank is disposed on a line perpendicularly bisecting the line connecting the centers of the rotatable member and the supporting member. By doing so, the sum of the radius of rotation of the free crank and the radius of rotation of the arm can be made small, so that bending and torsion of the free crank and the arm are small, and therefore, the weight saving is accomplished. By selecting a length of the free crank such that a swing range of the free crank does not overlap the moving range of the endless driving member, the free crank can be disposed closer to the center line of the bicycle or the like than the arm, thus accomplishing compact human powered drive mechanism.
In the case of bicycle, when the center of rotation of the free crank is disposed at a rear side of the pedal, hitting an obstruction can be avoided in rough road riding, and therefore, the arrangement is preferably employed in BMX (bicycle motocross) or the like intended for rough road riding. In the case of bicycles, when the axis of rotation of the free crank is disposed in a front side of the pedal, the large space in the front side of the pedal can be utilized, so that latitude of disposition of the arm and the crank is improved. In addition, the gravity center of the bicycle is shifted toward front side, so that rear wheel can be disposed in the front side, by which the wheelbase which is a distance between the centers of the front and rear wheels can be reduced, thus improving a rotation performance and an acceleration performance of the bicycle. It is known that by reducing the wheelbase, the rotation performance and the acceleration performance are remarkably improved. However, doing so results in the gravity center at a relatively rear position, so that there arises a problem that front wheel tends to rise during uphill riding or the like. For this reason, it has been difficult to make the wheelbase shorter than the present length.
In the case of tricycle, four-wheel-cycle, wheelchair or the like, in which a maneuvering handle (this term is used for a steering handle for the purpose of distinction from the handle functioning as the drive receiving portion) is operated by one of the hands, and the driving force is applied through the handle by the other hand, preferably the human powered drive mechanism is arranged under the driver""s arm outside the driver (the side of the driver) disposed slightly foreside of the driver with lower side ahead inclined center line connecting the centers of the rotatable member and the supporting member which constitute a pair. By this, the motion of the arm of the rider is smooth, and therefore, the riders weight can be easily applied to the arm with less fatigue.
In a further example, tightening means for normally tightening the chain is used. The constraining means comprising the arm and the free crank is effective to prevent the chain from deviating out of the regular moving plane and/or to prevent it from deforming, but it is not effective to prevent the chain from deviating from the oval orbit within the regular moving plane. With the structure of the present invention, the pulling force is directly applied to the chain link. If the chain is loose, the chain snakes at the linear portion of the oval orbit by the pulling, and at the sprocket portion, the rollers of the chain might be disengaged from the teeth of the sprocket. If it happens, the power loss is large, and the rollers and pins of the chain may be worn shortly. The tightening means for the chain preferably includes cylindrical members such as pipes to which the rotatable member and the supporting member are mounted, respectively, and the cylinders are telescoped for vertical sliding motion relative to each other, and a spring compressed between bottom plates of the cylinders. The tightening means may be studs, bolts or a combination thereof or the like to urge the cylinders vertically away from each other so as to tighten the chain.
Alternatively, an idle sprocket, idle roller or the like may be additionally provided, and a spring or the like for tightening the chain.
Generally, a damage in a chain drive mechanism relatively frequently occurs by the rollers or the link plates of the chain hitting the sprocket when the chain is moving on the sprocket. In view of this, there may be provided a guiding roller preferably coaxial with the pedal shaft or the handle shaft may be provided adjacent to the connecting portion between the chain and the pedal or the handle, and a rolling rail on which the guiding roller rolls and which covers at least a part of at least the lower one of the rotatable member and the supporting member, so as to prevent the rollers of the chain from disengaging from the teeth of the sprocket. In a preferable example of the human powered drive mechanism, the chain having the pedal or handle is provided at each of left and right sides. The right-hand side chain is trained on the first rotatable member and the first supporting member, and the left side chain is trained on the second rotatable member and the second supporting member; the first and second rotatable members are fixed to a common shaft. The third rotatable member in the form of a chain ring is fixed to the common shaft between the first and second rotatable member. The power applied to the left and right pedals or handles is transmitted to the chain ring through the left and right chains and the first or second rotatable member, and the power is further transmitted to the driving wheel (rear wheel in the case of the bicycle, or water wheel, propeller or the like in the case of boat) through the chain connected to the chain ring and the gear or the like. The supporting member may be in the form of a guiding rail having a width slightly smaller than the inner width of the link plates in the chain with the rollers of the chain rolling on the rail. In this case, the structure is simple with larger latitude of arrangement. When the supporting member is in the form of a rotatable member, the friction loss is smaller.
Further preferably, the left and right pedals and handles are phase-shifted by approx one half period. By doing so, the legs or the arms are used alternately, so that power can be applied continuously with smaller variation of rotation of the common shaft, and the force can be applied stably and uniformly, and therefore, less fatigue of the rider is expected. Here, the assembly comprising the chain and the rotatable member and the supporting member constituting a pair and engaging with the chain is called xe2x80x9chuman powered drive unitxe2x80x9d for simplicity of explanation. As regards the positions of the seat and the human powered drive units which are parallel to each other, the seat may be disposed in the middle of the human powered drive units, in the rear middle, in the front middle (the rider sits facing rearward and kick the pedals or pull the handles as in boat race), in the upper middle (normal in the case of bicycles) or in lower middle. A proper arrangement and an inclination angle of the human-powered drive unit is selected in consideration of the easy application of forces to the human powered drive receiving portions by the legs or arms of the rider.
In one example of the bicycle of the present invention, the human powered drive units which are substantially parallel to each other are disposed below the seat and inclined top side ahead. With this structure, the driver grips the maneuvering handle and kicks down the pedal rearward, so that pedal can be kicked using the muscle gluteus and back muscles, and therefore, high power can be imparted to the pedal.
In another example, the substantially parallel human powered drive units are disposed below the seat at slightly frontward positions such that linear orbit portion of the chain at the power phase is inclined bottom side ahead. With such a structure, as the rider can take a position that he or she pulls the maneuvering handle with the hands and kicks down the pedal the pedal can be kicked using the gluteus and back muscles, and therefore, high power can be imparted to the pedals.
In a further example, the substantially parallel human powered drive units are disposed below the seat, and the linear orbit portion of the chain at the power phase extends vertically. With this structure, the rider can easily apply all of his or her weight on the pedal, so that it is preferable for uphill riding.
In a preferable example of the human powered drive mechanism, the chain having the pedal or handle is disposed at each of the left and right sides; the right-hand side chain is trained on the first rotatable member and the first supporting member; the left side chain is trained on the second rotatable member and the second supporting member; and the first rotatable member and the second rotatable member are coaxial with the propulsion wheel (the front wheel or rear wheel in the case of bicycle, or the water wheel or propeller or the like in the case of boat). For example, in the case of bicycle, the first rotatable member and the second rotatable member have shaft which is common to the front wheel or the rear wheel, or they are made coaxial using a planetary gear transmission.
In a preferable example of the human powered drive mechanism of the present invention, an inclination angle of a large curvature radius portion of said endless driving member relative to the ground is variable.
With this structure applied to the bicycle, a vertical arrangement in which the large curvature radius portion of the human powered drive mechanism is close to the vertical line, is used during the uphill riding to efficiently apply the rider""s weight on the pedals, and the slanted arrangement is used during long distance riding on a flat road, with which the rider can sit on the seat and kicks the pedals forward or backward, thus efficiently using the riders weight, the muscles of the back, loins and legs can be effectively used.
In another preferable example of the human powered drive mechanism according to the present invention, the endless driving member is a chain including a plurality of links connected with pins, one of the links constitutes a driving force receiving link, which is provided with a shaft projected in the direction perpendicular to a plane in which the chain moves, and the driving force receiving link is rotatably mounted to the constraining means through the shaft. In this case, the driving force receiving link is provided with a U-shaped groove which is rotatably connected with adjacent links of the chain. When a timing belt is used, a unit including adjacent two teeth and roots corresponds to the link, and the tooth of the adjacent link is inserted into the U-shaped groove of the driving force receiving link at both sides, and they are rotatably collected by a pin penetrating the U-shaped groove. When a bead belt or a pinned belt is used, a unit including adjacent beads or pins correspond to a link, and the present invention is applicable.
In the foregoing description, a bicycle is taken as an example, but the present invention is applicable to another vehicles or like equipment such as a tricycle, a four-wheel-cycle, a wheelchair, a boat, a human powered plane, a training equipment or the like. According to this invention, the power input is increased so that speed and the torque can be increased thus accomplishing comfortable propulsion of the human powered vehicle. When the present invention is applied to the training equipment, the builder-upper equipment which is similar to a bicycle or boat is provided. When the large curvature radius portion of the human powered-drive mechanism is positioned vertically, and the distance between the centers of the rotatable member and the supporting member is made smaller, thus reducing the pedal stroke, and the motions of the feet and the loins are quite like those during walking, so that present invention is applicable to a walk training machine for rehabilitation of people hard to walk. The human powered drive receiving portion may be a pedal kicked by foot or a handle operated by a hand. In the case of tricycle, four-wheel-cycles, boats or the like, with which the rider can sit deeply, the large curvature radius portion of the endless driving member extended around the rotatable member and the supporting member constituting the pair, is inclined such that front part takes a lower position, and the seat is disposed substantially at the same level as a higher one of the rotatable member and the supporting member at a rear part of the human powered drive mechanism. Additionally, a backrest may be provided. With the backrest, the rider easily apply force to the pedals, and therefore, the present invention is conveniently used. The present invention is not limited to the case where the human powered drive units are disposed at left and right sides, respectively, wherein the phases of the human powered drive receiving portions are deviated by xc2xd period. For example, in the case of the tricycle, the four-wheel-cycle, the boat or the like, the human powered drive mechanisms of the present invention are substantially horizontally disposed at the lateral sides of the rider on the seat to the level of the riders loins to shoulder, wherein the phases of the left and right units are aligned to each other.
The human powered drive mechanism of the present invention is applicable to the vehicles or like equipment such as a tricycle, a four-wheel-cycle, a wheel chair, a boat, a human powered plane, a training equipment or the like, and the human power can be efficiently converted to torque, so that significant output increase is accomplished, and therefore, a powerless rider can ride a long distance. When the present invention is applied to the bicycle or the wheel chair, the uphill riding performance, the characteristics for evading danger or the like is remarkably improved.